Biology subjects

Murray, D. T.

Publications and source records attributed to Murray, D. T..

3 recordsLinked to original sources

bioRxiv2021

Identification of the Rigid Core for Aged Liquid Droplets of the TDP-43 Low Complexity Domain

The biomolecular condensation of proteins with low complexity sequences plays a functional role in RNA metabolism and a pathogenic role in neurodegenerative diseases. The formation of dynamic liquid droplets brings biomolecules together to achieve complex cellular functions. The rigidification of liquid droplets into {beta}-strand-rich hydrogel structures composed of protein fibrils is thought to be purely pathological in nature. However, low complexity sequences often harbor multiple fibril-prone regions with delicately balanced functional and pathological interactions. Here, we investigate the maturation of liquid droplets formed by the low complexity domain of the TAR DNA-binding protein 43 (TDP-43). Solid state nuclear magnetic resonance measurements on the aged liquid droplets identify a structured core region distinct from the region thought to be most important for pathological fibril formation and aggregation. The results of this study show that multiple segments of this low complexity domain are prone to form fibrils, and that stabilization of {beta}-strand-rich structure in one segment precludes the other region from adopting rigid fibril structure. Table of Contents Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=137 SRC="FIGDIR/small/433427v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@5b0decorg.highwire.dtl.DTLVardef@1ef3887org.highwire.dtl.DTLVardef@684f0aorg.highwire.dtl.DTLVardef@1d23fd_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2020

Small-angle neutron scattering solution structures of NADPH-dependent sulfite reductase

Sulfite reductase (SiR), a dodecameric complex of flavoprotein reductase subunits (SiRFP) and hemoprotein oxidase subunits (SiRHP), reduces sulfur reduction for biomass incorporation. Electron transfer within SiR requires intra- and inter-subunit interactions that are mediated by the relative position of each protein, governed by flexible domain movements. Using small-angle neutron scattering, we report the first solution structures of SiR heterodimers containing a single copy of each subunit. These structures show how the subunits bind and how both subunit binding and oxidation state impact SiRFPs conformation. Neutron contrast matching experiments on selectively deuterated heterodimers allow us to define the contribution of each subunit to the solution scattering. SiRHP binding induces a change in the position of SiRFPs flavodoxin-like domain relative to its ferredoxin-NADP+ reductase domain while compacting SiRHPs N-terminus. Reduction of SiRFP leads to a more open structure relative to its oxidized state, re-positioning SiRFPs N-terminal flavodoxin-like domain towards the SiRHP binding position. These structures show, for the first time, how both SiRHP binding to, and reduction of, SiRFP positions SiRFP for electron transfer between the subunits.

biochemistry↗

bioRxiv2020

Dynamic structural order of a low complexity domain facilitates assembly of intermediate filaments

The coiled-coil domains of intermediate filament (IF) proteins are flanked by regions of low sequence complexity. Whereas IF coiled-coil domains assume dimeric and tetrameric conformations on their own, maturation of eight tetramers into cylindrical IFs is dependent upon either "head" or "tail" domains of low sequence complexity. Here we confirm that the tail domain required for assembly of Drosophila Tm1 IFs functions by forming labile cross-{beta} interactions. These interactions are seen in polymers made from the tail domain alone as well as assembled IFs formed by the intact Tm1 protein. The ability to visualize such interactions in situ within the context of a discrete cellular assembly lends support to the concept that equivalent interactions may be used in organizing other dynamic aspects of cell morphology. One Sentence SummaryA new form of protein folding that interconverts between the structured and unstructured states controls assembly of intermediate filaments.

biochemistry↗